1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member and also to an electrophotographic apparatus and a facsimile machine using the electrophotographic photosensitive member. More particularly, the present invention is concerned with an electrophotographic photosensitive member having a photosensitive layer formed of a material containing a disazo dye having a specific structure, as well as an electrophotographic apparatus and a facsimile machine using such electrophotographic photosensitive member.
2. Description of the Related Arts
Hitherto, various types of organic photoconductive materials for use in electrophotographic photosensitive members have been known, such as photoconductive polymers represented by poly-N-vinylcarbazole, low-molecular organic photoconductive materials represented by 2,5-bis(p-diethylaminophenyl)- 1,3,4-osadiazole, and mixtures of such organic photoconductive materials and various dyes or pigments.
In general, an electrophotographic photosensitive member using an organic photoconductive material offers advantages such as very high yield and comparatively low cost of production, as well as ease of control of color sensitivity through selection of a dye or pigment used therein. Therefore, various studies have been made on this type of electrophotographic photosensitive member. In particular, a new type of photosensitive member, generally referred to as "function-separation type photosensitive member", has been successfully developed lately. This type of photosensitive member has a laminate photoconductive layer composed of a charge generating layer containing an organic photoconductive dye or pigment and a charge transporting layer containing the aforementioned photoconductive polymer or low-molecular organic photoconductive material. It has been confirmed that this type of photosensitive member offers remarkable improvements over known organic electrophotographic photosensitive members which were still unsatisfactory in sensitivity and durability.
Among various known organic photosensitive materials, azo pigments are notable because of superiority in photoconductivity. In addition, various compounds having various characteristics can easily be prepared by using various combinations of the azo component and the coupler component. For example, compounds are proposed and disclosed in Japanese Patent Unexamined Patent Publication Nos. 57-138646, 57-202349 and 63-282743.
The current trends for higher image quality and higher durability of electrophotographic apparatuses have given a rise to the demand for an electrophotographic photosensitive member which has still higher sensitivity and greater stability of electrophotographic characteristics against repeated use.